Additive Manufacturing of Bone Scaffolds Using PolyJet and Stereolithography Techniques

In this study, the printing capability of two different additive manufacturing (3D printing) techniques, namely PolyJet and micro-stereolithography (µSLA), are investigated regarding the fabrication of bone scaffolds. The 3D-printed scaffold structures are used as supports in replacing and repairing fractured bone tissue. Printed bone scaffolds with complex structures produced using additive manufacturing technology can mimic the mechanical properties of natural human bone, providing lightweight structures with modifiable porosity levels. In this study, 3D scaffold structures are designed with different combinations of architectural parameters. The dimensional accuracy, permeability, and mechanical properties of complex 3D-printed scaffold structures are analyzed to compare the advantages and drawbacks associated with the two techniques. The fluid flow rates through the 3D-printed scaffold structures are measured and Darcy’s law is applied to calculate the experimentally measured permeability. The Kozeny–Carman equation is applied for theoretical calculation of permeability. Compression tests were performed on the printed samples to observe the effects of the printing techniques on the mechanical properties of the 3D-printed scaffold structures. The effect of the printing direction on the mechanical properties of the 3D-printed scaffold structures is also analyzed. The scaffold structures printed with the µSLA printer demonstrate higher permeability and mechanical properties as compared to those printed using the PolyJet technique. It is demonstrated that both the µSLA and PolyJet printing techniques can be used to print 3D scaffold structures with controlled porosity levels, providing permeability in a similar range to human bone.

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Additive Manufacturing of PLA-Based Composites Using Fused Filament Fabrication: Effect of Graphene Nanoplatelet Reinforcement on Mechanical Properties, Dimensional Accuracy and Texture

Polymers ◽

10.3390/polym11050799 ◽

2019 ◽

Vol 11 (5) ◽

pp. 799 ◽

Cited By ~ 41

Author(s):

Miguel Caminero ◽

Jesús Chacón ◽

Eustaquio García-Plaza ◽

Pedro Núñez ◽

José Reverte ◽

...

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

Impact Strength ◽

Dimensional Accuracy ◽

Fused Filament Fabrication ◽

Graphene Nanoplatelet ◽

Graphene Composite ◽

General Terms ◽

3D Printed ◽

Composite Samples

Fused filament fabrication (FFF) is a promising additive manufacturing (AM) technology due to its ability to build thermoplastics parts with advantages in the design and optimization of models with complex geometries, great design flexibility, recyclability and low material waste. This technique has been extensively used for the manufacturing of conceptual prototypes rather than functional components due to the limited mechanical properties of pure thermoplastics parts. In order to improve the mechanical performance of 3D printed parts based on polymeric materials, reinforcements including nanoparticles, short or continuous fibers and other additives have been adopted. The addition of graphene nanoplatelets (GNPs) to plastic and polymers is currently under investigation as a promising method to improve their working conditions due to the good mechanical, electrical and thermal performance exhibited by graphene. Although research shows particularly promising improvement in thermal and electrical conductivities of graphene-based nanocomposites, the aim of this study is to evaluate the effect of graphene nanoplatelet reinforcement on the mechanical properties, dimensional accuracy and surface texture of 3D printed polylactic acid (PLA) structures manufactured by a desktop 3D printer. The effect of build orientation was also analyzed. Scanning Electron Microscope (SEM) images of failure samples were evaluated to determine the effects of process parameters on failure modes. It was observed that PLA-Graphene composite samples showed, in general terms, the best performance in terms of tensile and flexural stress, particularly in the case of upright orientation (about 1.5 and 1.7 times higher than PLA and PLA 3D850 samples, respectively). In addition, PLA-Graphene composite samples showed the highest interlaminar shear strength (about 1.2 times higher than PLA and PLA 3D850 samples). However, the addition of GNPs tended to reduce the impact strength of the PLA-Graphene composite samples (PLA and PLA 3D850 samples exhibited an impact strength about 1.2–1.3 times higher than PLA-Graphene composites). Furthermore, the addition of graphene nanoplatelets did not affect, in general terms, the dimensional accuracy of the PLA-Graphene composite specimens. In addition, PLA-Graphene composite samples showed, in overall terms, the best performance in terms of surface texture, particularly when parts were printed in flat and on-edge orientations. The promising results in the present study prove the feasibility of 3D printed PLA-graphene composites for potential use in different applications such as biomedical engineering.

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Influence of printing direction on 3D printed ABS specimens

Production Engineering Archives ◽

10.30657/pea.2020.26.24 ◽

2020 ◽

Vol 26 (3) ◽

pp. 127-130

Author(s):

Nassim Markiz ◽

Eszter Horváth ◽

Péter Ficzere

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Additive Manufacturing ◽

Ultimate Tensile Strength ◽

Modulus Of Elasticity ◽

Tensile Tests ◽

Standard Test ◽

Complex Objects ◽

3D Printed ◽

Printing Direction

AbstractIn the recent years, additive manufacturing became an interesting topic in many fields due to the ease of manufacturing complex objects. However, it is impossible to determine the mechanical properties of any additive manufacturing parts without testing them. In this work, the mechanical properties with focus on ultimate tensile strength and modulus of elasticity of 3D printed acrylonitrile butadi-ene styrene (ABS) specimens were investigated. The tensile tests were carried using Zwick Z005 loading machine with a capacity of 5KN according to the American Society for Testing and Materials (ASTM) D638 standard test methods for tensile properties of plastics. The aim of this study is to investigate the influence of printing direction on the mechanical properties of the printed specimens. Thus, for each printing direction ( and ), five specimens were printed. Tensile testing of the 3D printed ABS specimens showed that the printing direction made the strongest specimen at an ultimate tensile strength of 22 MPa while at printing direction it showed 12 MPa. No influence on the modulus of elasticity was noticed. The experimental results are presented in the manuscript.

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Load Distribution on PET-G 3D Prints of Honeycomb Cellular Structures under Compression Load

Polymers ◽

10.3390/polym13121983 ◽

2021 ◽

Vol 13 (12) ◽

pp. 1983

Author(s):

Olimpia Basurto-Vázquez ◽

Elvia P. Sánchez-Rodríguez ◽

Graham J. McShane ◽

Dora I. Medina

Keyword(s):

Fused Deposition Modeling ◽

Structural Characteristics ◽

Honeycomb Structure ◽

Cellular Structures ◽

Displacement Curve ◽

Compression Tests ◽

Compression Load ◽

Fused Deposition ◽

3D Printed ◽

Printing Direction

Energy resulting from an impact is manifested through unwanted damage to objects or persons. New materials made of cellular structures have enhanced energy absorption (EA) capabilities. The hexagonal honeycomb is widely known for its space-filling capacity, structural stability, and high EA potential. Additive manufacturing (AM) technologies have been effectively useful in a vast range of applications. The evolution of these technologies has been studied continuously, with a focus on improving the mechanical and structural characteristics of three-dimensional (3D)-printed models to create complex quality parts that satisfy design and mechanical requirements. In this study, 3D honeycomb structures of novel material polyethylene terephthalate glycol (PET-G) were fabricated by the fused deposition modeling (FDM) method with different infill density values (30%, 70%, and 100%) and printing orientations (edge, flat, and upright). The effectiveness for EA of the design and the effect of the process parameters of infill density and layer printing orientation were investigated by performing in-plane compression tests, and the set of parameters that produced superior results for better EA was determined by analyzing the area under the curve and the welding between the filament layers in the printed object via FDM. The results showed that the printing parameters implemented in this study considerably affected the mechanical properties of the 3D-printed PET-G honeycomb structure. The structure with the upright printing direction and 100% infill density exhibited an extension to delamination and fragmentation, thus, a desirable performance with a long plateau region in the load–displacement curve and major absorption of energy.

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Fabrication of Polycaprolactone/Nano Hydroxyapatite (PCL/nHA) 3D Scaffold with Enhanced In Vitro Cell Response via Design for Additive Manufacturing (DfAM)

Polymers ◽

10.3390/polym13091394 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1394

Author(s):

Yong Sang Cho ◽

So-Jung Gwak ◽

Young-Sam Cho

Keyword(s):

Mechanical Properties ◽

Cell Response ◽

Structural Characteristics ◽

Structure Design ◽

Compressive Modulus ◽

Control Group ◽

Design For Additive Manufacturing ◽

3D Scaffold ◽

3D Printed

In this study, we investigated the dual-pore kagome-structure design of a 3D-printed scaffold with enhanced in vitro cell response and compared the mechanical properties with 3D-printed scaffolds with conventional or offset patterns. The compressive modulus of the 3D-printed scaffold with the proposed design was found to resemble that of the 3D-printed scaffold with a conventional pattern at similar pore sizes despite higher porosity. Furthermore, the compressive modulus of the proposed scaffold surpassed that of the 3D-printed scaffold with conventional and offset patterns at similar porosities owing to the structural characteristics of the kagome structure. Regarding the in vitro cell response, cell adhesion, cell growth, and ALP concentration of the proposed scaffold for 14 days was superior to those of the control group scaffolds. Consequently, we found that the mechanical properties and in vitro cell response of the 3D-printed scaffold could be improved by kagome and dual-pore structures through DfAM. Moreover, we revealed that the dual-pore structure is effective for the in vitro cell response compared to the structures possessing conventional and offset patterns.

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Additive manufacturing of PLA-based scaffolds intended for bone regeneration and strategies to improve their biological properties

e-Polymers ◽

10.1515/epoly-2020-0046 ◽

2020 ◽

Vol 20 (1) ◽

pp. 571-599

Author(s):

Ricardo Donate ◽

Mario Monzón ◽

María Elena Alemán-Domínguez

Keyword(s):

Mechanical Properties ◽

Tissue Engineering ◽

Additive Manufacturing ◽

Bone Regeneration ◽

Polylactic Acid ◽

State Of The Art ◽

Biological Properties ◽

Design Stage ◽

Bone Scaffolds ◽

Regeneration Of Bone

AbstractPolylactic acid (PLA) is one of the most commonly used materials in the biomedical sector because of its processability, mechanical properties and biocompatibility. Among the different techniques that are feasible to process this biomaterial, additive manufacturing (AM) has gained attention recently, as it provides the possibility of tuning the design of the structures. This flexibility in the design stage allows the customization of the parts in order to optimize their use in the tissue engineering field. In the recent years, the application of PLA for the manufacture of bone scaffolds has been especially relevant, since numerous studies have proven the potential of this biomaterial for bone regeneration. This review contains a description of the specific requirements in the regeneration of bone and how the state of the art have tried to address them with different strategies to develop PLA-based scaffolds by AM techniques and with improved biofunctionality.

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Effect of Porosity on Mechanical Properties of 3D Printed Polymers: Experiments and Micromechanical Modeling Based on X-Ray Computed Tomography Analysis

Polymers ◽

10.3390/polym11071154 ◽

2019 ◽

Vol 11 (7) ◽

pp. 1154 ◽

Cited By ~ 27

Author(s):

Wang ◽

Zhao ◽

Fuh ◽

Lee

Keyword(s):

Computed Tomography ◽

Mechanical Properties ◽

Additive Manufacturing ◽

Fused Deposition Modeling ◽

Micromechanical Model ◽

Micromechanical Modeling ◽

X Ray ◽

Fused Deposition ◽

3D Printed ◽

X Ray Computed

Additive manufacturing (commonly known as 3D printing) is defined as a family of technologies that deposit and consolidate materials to create a 3D object as opposed to subtractive manufacturing methodologies. Fused deposition modeling (FDM), one of the most popular additive manufacturing techniques, has demonstrated extensive applications in various industries such as medical prosthetics, automotive, and aeronautics. As a thermal process, FDM may introduce internal voids and pores into the fabricated thermoplastics, giving rise to potential reduction on the mechanical properties. This paper aims to investigate the effects of the microscopic pores on the mechanical properties of material fabricated by the FDM process via experiments and micromechanical modeling. More specifically, the three-dimensional microscopic details of the internal pores, such as size, shape, density, and spatial location were quantitatively characterized by X-ray computed tomography (XCT) and, subsequently, experiments were conducted to characterize the mechanical properties of the material. Based on the microscopic details of the pores characterized by XCT, a micromechanical model was proposed to predict the mechanical properties of the material as a function of the porosity (ratio of total volume of the pores over total volume of the material). The prediction results of the mechanical properties were found to be in agreement with the experimental data as well as the existing works. The proposed micromechanical model allows the future designers to predict the elastic properties of the 3D printed material based on the porosity from XCT results. This provides a possibility of saving the experimental cost on destructive testing.

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EFFECT OF EXTRUSION PROCESS PARAMETERS ON MECHANICAL PROPERTIES OF 3D PRINTED PLA PRODUCT

Journal of Mechanical Engineering and Mechatronics ◽

10.33021/jmem.v6i2.1573 ◽

2021 ◽

Vol 6 (2) ◽

pp. 119

Author(s):

Nanang Ali Sutisna ◽

Rakha Amrillah Fattah

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

Fused Deposition Modeling ◽

Extrusion Process ◽

Experimental Procedure ◽

Fused Deposition ◽

Novel Approach ◽

Deposition Modeling ◽

3D Printed ◽

3D Digital Models

The method of producing items through synchronously depositing material level by level, based on 3D digital models, is named Additive Manufacturing (AM) or 3D-printing. Amongs many AM methods, the Fused Deposition Modeling (FDM) technique along with PLA (Polylactic acid) material is commonly used in additive manufacturing. Until now, the mechanical properties of the AM components could not be calculated or estimated until they've been assembled and checked. In this work, a novel approach is suggested as to how the extrusion process affects the mechanical properties of the printed component to obtain how the parts can be manufactured or printed to achieve improved mechanical properties. This methodology is based on an experimental procedure in which the combination of parameters to achieve an optimal from a manufacturing experiment and its value can be determined, the results obtained show the effect of the extrusion process affects the mechanical properties.

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DLP 3D Printing Meets Lignocellulosic Biopolymers: Carboxymethyl Cellulose Inks for 3D Biocompatible Hydrogels

Polymers ◽

10.3390/polym12081655 ◽

2020 ◽

Vol 12 (8) ◽

pp. 1655 ◽

Cited By ~ 4

Author(s):

Giuseppe Melilli ◽

Irene Carmagnola ◽

Chiara Tonda-Turo ◽

Fabrizio Pirri ◽

Gianluca Ciardelli ◽

...

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

3D Printing ◽

Carboxymethyl Cellulose ◽

Biomedical Applications ◽

Digital Light Processing ◽

Chemically Modified ◽

Significant Step ◽

3D Printed ◽

Biomedical Field

The development of new bio-based inks is a stringent request for the expansion of additive manufacturing towards the development of 3D-printed biocompatible hydrogels. Herein, methacrylated carboxymethyl cellulose (M-CMC) is investigated as a bio-based photocurable ink for digital light processing (DLP) 3D printing. CMC is chemically modified using methacrylic anhydride. Successful methacrylation is confirmed by 1H NMR and FTIR spectroscopy. Aqueous formulations based on M-CMC/lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) photoinitiator and M-CMC/Dulbecco’s Modified Eagle Medium (DMEM)/LAP show high photoreactivity upon UV irradiation as confirmed by photorheology and FTIR. The same formulations can be easily 3D-printed through a DLP apparatus to produce 3D shaped hydrogels with excellent swelling ability and mechanical properties. Envisaging the application of the hydrogels in the biomedical field, cytotoxicity is also evaluated. The light-induced printing of cellulose-based hydrogels represents a significant step forward in the production of new DLP inks suitable for biomedical applications.

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Superior Mechanical Behavior and Fretting Wear Resistance of 3D-Printed Inconel 625 Superalloy

Applied Sciences ◽

10.3390/app8122439 ◽

2018 ◽

Vol 8 (12) ◽

pp. 2439 ◽

Cited By ~ 8

Author(s):

Yong Gao ◽

Mingzhuo Zhou

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Wear Resistance ◽

Additive Manufacturing ◽

High Hardness ◽

Fretting Wear ◽

Inconel 625 ◽

3D Printed ◽

Inconel 625 Superalloy ◽

Electron Beam Selective Melting

Additive manufacturing (AM) nickel-based superalloys have been demonstrated to equate or exceed mechanical properties of cast and wrought counterparts but their tribological potentials have not been fully realized. This study investigates fretting wear behaviors of Inconel 625 against the 42 CrMo4 stainless steel under flat-on-flat contacts. Inconel 625 is prepared by additive manufacturing (AM) using the electron beam selective melting. Results show that it has a high hardness (335 HV), superior tensile strength (952 MPa) and yield strength (793 MPa). Tribological tests indicate that the AM-Inconel 625 can suppress wear of the surface within a depth of only ~2.4 μm at a contact load of 106 N after 2 × 104 cycles. The excellent wear resistance is attributed to the improved strength and the formation of continuous tribo-layers containing a mixture of Fe2O3, Fe3O4, Cr2O3 and Mn2O3.

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GEOMETRY AND MECHANICAL PROPERTIES OF A 3D-PRINTED TITANIUM MICROSTRUCTURE

Acta Polytechnica CTU Proceedings ◽

10.14311/app.2018.15.0104 ◽

2018 ◽

Vol 15 ◽

pp. 104-108

Author(s):

Luboš Řehounek ◽

Petra Hájková ◽

Petr Vakrčka ◽

Aleš Jíra

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Uniaxial Compression ◽

Elastic Moduli ◽

Weight Ratio ◽

Porous Structures ◽

Compression Tests ◽

Local Material ◽

3D Printed ◽

Titanium Microstructure

Construction applications sometimes require use of a material other than construction steel or concrete – mainly in cases, where strength to weight ratio needs to be considered. A suitable solution to this problem are structures manufactured using the 3D printing process, as they have a very good strength to weight ratio (i.e.: Ti-6Al-4V – σ<sub>ult</sub> = 900 MPa and ρ = 4500 kg/m<sup>3</sup>). Trabecular structures are porous structures with local material characteristics identical to their commonly manufactured counterparts, but due to their geometry, they have different global mechanical properties and are suited for special applications. We designed and manufactured six variants of these structures and subjected them to uniaxial compression tests, nanoindentation tests and subsequently evaluated their differences and elastic moduli. The values of global moduli E are in the range of 2.55 GPa – 3.55 GPa for all specimens.

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